Fluid reservoir with level measurement and a dosing system, a withdrawal system and a combined dosing/withdrawal system

ABSTRACT

A liquid reservoir with level measurement includes a base body ( 10 ) and a channel ( 12 ) implemented in the base body and comprising an inlet ( 14 ) and an outlet ( 16 ), the dimensions of the cross-section of the channel being selected such that a liquid ( 18 ) which may be filled into the channel forms a liquid meniscus ( 20 ) which demarcates a section ( 12   b ) of the channel which is filled with liquid from an unfilled section ( 12   a ) of the channel in which no liquid is present, the position of the meniscus in relation to the channel being substantially independent of the orientation of the liquid reservoir. The liquid reservoir further includes detection means ( 32, 22, 24 ) for detecting the position of the liquid meniscus and/or the channel so as to obtain, from the position of the liquid meniscus, the level and/or a change in the level of the liquid reservoir. The inventive liquid reservoir is suitable as a low-priced drug reservoir particularly in connection with a capacitive level detection.

FIELD OF THE INVENTION

The present invention relates to a liquid reservoir and in particular toa liquid reservoir with level measurement which may be used inconnection with a dosing system, a withdrawal system or a dosingsystem/withdrawal system.

BACKGROUND OF THE INVENTION AND PRIOR ART

In the field of medicine but also in other fields of technology there isa need for determining amounts of liquid so as to carry out an absoluteliquid measurement or to dose certain amounts of liquid. For determiningthe amount of liquid dispensed, it is no longer the amount of liquid perse that is decisive but the change in the amount of liquid over time.

Particularly in the field of medicine there is also a strong need forliquid reservoirs for drugs. Here it is often required to administeraccurately dosed amounts of liquid. In addition, there is a requirementthat the liquid reservoirs are designed in a low-cost manner since theyare often disposable articles which cannot be reused for hygienicreasons.

In the U.S. Pat. No. 5,463,228, an apparatus for an automatic exactdosing of small amounts of liquid in a medical analysis system isdisclosed, the apparatus comprising a transparent measuring tube with acapillary tube having an internal diameter of less than 1 mm, themeasuring tube further comprising a liquid transfer opening at one endof same, the liquid transfer opening being provided for drawing in aliquid. The apparatus further includes liquid phase boundary detectionmeans for automatic detection of a liquid phase boundary in themeasuring tube, an electrical position signal of a position of theliquid phase boundary being generated. The detection of the liquid phaseboundary takes place in an optical manner, to be precise using a lightsource and a CCD line array.

In DE 4306061 A1, an apparatus for detecting the level of a capillaryoverflow channel is disclosed. The apparatus includes a channelconnected, at one end, to an inflow which is connected to a reservoirvia a controllable valve. At the other end of the channel there is afurther channel of a larger diameter which is connected to an outflow.An overflow channel which is designed in a helical manner around thechannel and which extends between a first detection electrode and asecond detection electrode is in fluidic communication with the channelso as to capacitively detect the level of the overflow channel. Theoverflow channel acts as a buffer volume. If a level is detected in theoverflow channel, the valve between the reservoir and the inflow isclosed until it is detected that the overflow channel is empty. Then thevalve is opened again until the overflow channel again has a level,whereupon the valve is closed again. The control device may be employedfor separating an ink reservoir in plotter pens, recording devices,medical apparatus or apparatus used in process engineering.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a dosing system or acombined dosing/withdrawal system with a liquid reservoir.

In accordance with a first aspect of the invention, this object isachieved by a dosing system, comprising: a liquid reservoir with levelmeasurement, the liquid reservoir comprising: a base body; a channelimplemented in the base body and having an inlet and an outlet, thedimensions of a cross-section of the channel being selected such that aliquid which may be filled into the channel forms a liquid meniscuswhich demarcates a section of the channel filled with liquid from anunfilled section of the channel in which no liquid is present, theposition of the liquid meniscus in relation to the channel beingsubstantially independent of the orientation of the liquid reservoir;and detection means for detecting the position of the liquid meniscus inrelation to the channel so as to obtain the level and/or a change in thelevel of the liquid reservoir from the position of the liquid meniscus;means for exhausting a liquid which may be filled into the liquidreservoir, the means for exhausting being connected to the outlet,and/or means for pumping gas into the unfilled section of the channel,the means for pumping being connected to the inlet; and control meansfor controlling the means for exhausting and/or the means for pumping,the control means being coupled to the detection means of the liquidreservoir so as to dispense a predetermined amount of liquid from thechannel via the outlet of the channel, depending on the position of theliquid meniscus; wherein the detection means are capacitive and comprisetwo electrodes electrically insulated from each other and mounted on thebase body such that both the filled and the unfilled section of thechannel extend between same, whereby an electric field that may begenerated between the two electrodes is present both in the filledsection of the channel and in the unfilled section of the channel, andwhereby a change in the position of the liquid meniscus leads to aproportional change in capacitance.

In accordance with a second aspect of the invention, this object isachieved by a combined dosing/withdrawal system, comprising: a liquidreservoir with level measurement, the liquid reservoir comprising: abase body; a channel implemented in the base body and having an inletand an outlet, the dimensions of the channel cross-section beingselected such that a liquid which may be filled into the channel forms aliquid meniscus which demarcates a section of the channel filled withliquid from an unfilled section of the channel in which no liquid ispresent, the position of the liquid meniscus in relation to the channelbeing substantially independent of the orientation of the liquidreservoir; and detection means for detecting the position of the liquidmeniscus in relation to the channel so as to obtain the level and/or achange in the level of the liquid reservoir from the position of theliquid meniscus; first means for pumping a liquid into the liquidreservoir and/or for exhausting a liquid from the liquid reservoir, thefirst means for pumping and/or exhausting being connected to the outlet,and/or second means for exhausting gas from the unfilled section of thechannel and/or for pumping gas into the unfilled section of the channel,the second means for exhausting and/or pumping being connected to theinlet; and control means for controlling the first means and/or thesecond means, the control means being coupled to the detection means ofthe liquid reservoir so as to convey a predetermined amount of liquidinto the channel via the outlet of the channel and/or dispense apredetermined amount of liquid from the channel via the outlet of thechannel, depending on the position of the liquid meniscus, wherein thedetection means are capacitive and comprise two electrodes electricallyinsulated from each other and mounted on the base body such that boththe filled and the unfilled section of the channel extend between same,whereby an electric field that may be generated between the twoelectrodes is present both in the filled section of the channel and inthe unfilled section of the channel, and whereby a change in theposition of the liquid meniscus leads to a proportional change incapacitance.

The present invention is based on the findings that accurate levelmeasurement of a liquid in a liquid reservoir may be achieved if theliquid reservoir comprises a channel implemented in a base body andhaving an inlet and an outlet, the dimensions of the cross-section ofthe channel being selected such that a liquid which may be filled intothe channel forms a liquid meniscus which demarcates a section of thechannel filled with liquid from an unfilled section of the channel, i.e.a section of the channel in which no liquid is present, the position ofthe meniscus in relation to the channel being substantially independentof the orientation of the liquid reservoir. For level measurement,detection means for detecting the position of the liquid meniscus inrelation to the channel are used so as to obtain the level and/or achange in the level of the liquid reservoir from the position of theliquid meniscus.

Generally speaking, the position and shape of the liquid meniscus aredependent on the gravity on the one hand as well as on the surfacetension between the liquid and air, and on the interfacial tensionbetween the drug and the reservoir material on the other hand. The lasttwo parameters define the wetting angle. In accordance with theinvention, the dimensions of the cross-section of the channel areselected to be so small that the shape of the liquid meniscus isdetermined, above all, by the surface and interfacial tensions and nolonger by the gravity or other forces, i.e. rotational force,vibrational force, magnetic forces etc. Depending on the liquidproperties and the channel material, the surface tension (and also theinterfacial tension) will be dominant relative to gravity in channelswhich are circular in cross-section and have diameters smaller than 0.5to 3 mm. Here gravity no longer is important, i.e. the liquid meniscuswill not significantly change its position even if the liquid reservoiris in any position desired, be it that same is tilted, upside down orarranged in any other way.

Depending on the implementation, a capacitive detection of the positionof the level meniscus in relation to the channel, or even opticaldetection as well as other detection means may be employed. Alldetection means are based on different properties of the unfilledsection of the channel as compared with the filled section of thechannel.

The present invention is particularly advantageous in that it may beimplemented in a very low-cost manner, in particular if capacitivedetection methods are used, since in this case only two electrodes mustbe mounted in relation to the channel, by which electrodes an electricfield may be generated which extends both in the unfilled section and inthe filled section of the channel. This advantage of low cost isrelevant in particular on the intensely competitive mass market ofdisposable products in the field of medicine.

The dosing system or the combined dosing/withdrawal system of thepresent invention includes a liquid reservoir whose level may bedetermined more accurately in a manner which is completely independentof the position and location of the liquid reservoir. This, in turn, ishighly important in liquid reservoirs for accommodating drugs, sincesuch liquid reservoirs are carried by patients, and hence constantlychange their position and orientation, in particular if such liquidreservoirs are used for constant dosing of drugs. Due to the inventivedimensioning of the channel, however, the liquid meniscus always staysin the same position, since its position no longer depends on gravitybut merely on the surface tension of the drug and on the interfacialtension between the drug and the channel wall.

A further advantage of the present invention is that the containervolume of the liquid reservoir may still take on considerable dimensionswith the inventive channel. This can be achieved, on the one hand, bythe fact that the channel is arranged in the base body in the shape of ameander, so that a maximum channel length results in comparison with theexternal dimensions of the base body. If space requirements for thecontainer are not decisive, it is alternatively also possible, inprinciple, to make the volume very large since the formation of ameniscus whose position in the channel is substantially independent ofgravity does not depend on the cross-sectional area of the channel buton the shape of the cross-section of the channel, more specifically onthe smallest dimension of the channel cross-section. If a rectangularchannel is considered, a meniscus will form whenever a side length ofthe channel cross-section is dimensioned to be so small that the surfacetension of the liquid leads to the formation of a meniscus. The otherside length of the channel cross-section, however, may basically take onindefinitely high values, so that the container volume of the liquidreservoir may be adjusted within broad limits. For practicalapplications, in particular in the field of drug dosing system, volumesin the range of 0.1 to 50 ml are sufficient, however, so that theinventive liquid reservoirs are still convenient.

A further advantage of the present invention is that, if the base bodyis implemented as a hose, a commercially available hose with acorrespondingly small cross-sectional diameter may easily be used as aliquid reservoir, since it must be supplemented merely by capacitivedetection means, for example, so as to achieve a low-cost, flexible andaccurate liquid reservoir.

It shall be pointed out that the dimensions of the channel cross-sectiondo not necessarily have to be consistent across the length of thechannel. Any increases or decreases in the cross-section may readily becalibrated out and/or taken into account via a conversion factor, whichis dependent on the meniscus position, in determining the level volume.

A further advantage of the present invention is that, due to therelatively small channel dimensions, the meniscus concept and acapacitive measurement principle complement each other in a nearlyoptimum manner. Generally speaking, the smaller the distance between thecapacitance electrodes, the higher a capacitance measured. Thus themeniscus also is the more stable, the smaller the dimensions of thechannel are. With regard to the capacitive measurement principle,however, this means that depending on the geometry and the dielectricparameters of the liquid and the reservoir material, a sufficiently highsensitivity occurs in the form of a sufficiently large change incapacitance in the movement of the meniscus, which is determined by adischarge of the liquid from the liquid reservoir.

A further advantage of the present invention is that by means oflow-cost but efficient concepts, the evaporation of the liquid in theliquid reservoir may be reduced or fully eliminated, depending on therequirements, without necessitating expensive measures.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be explained indetail below with reference to the accompanying figures, in which:

FIG. 1 shows a detailed representation of an inventive liquid reservoirwith level measurement using capacitive detection;

FIG. 2 shows a graphic representation of the course of capacitanceversus the meniscus position for the inventive liquid reservoir of FIG.1;

FIG. 3 a top view of a base body of an inventive liquid reservoir whichalso uses capacitive detection of the position of the meniscus, wherein,however, vertical electrodes are present;

FIG. 4 shows a top view of the bottom electrode and the cap electrode,which are each comprised of a plurality of individual electrodes in theembodiment shown in FIG. 4;

FIG. 5 shows a perspective view of an inventive liquid reservoir withlevel measurement, wherein the base body is implemented as a hose;

FIG. 6 shows a perspective view of an inventive liquid reservoir withlevel measurement, wherein the base body is also implemented as a hose,as in FIG. 5, wherein, however, a coaxial arrangement of the twoelectrodes is used; and

FIG. 7 shows a block diagram of the inventive dosing system, theinventive withdrawal system or the inventive combined dosing/withdrawingsystem.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an inventive liquid reservoir with level measurement,wherein the preferred capacitive detection principle is employed. Theinventive liquid reservoir includes a base body 10, wherein a preferablymeander-shaped channel 12 is formed which comprises an inlet 14 and anoutlet 16. The dimensions of the channel cross-section are selected suchthat a liquid 18 which may be filled into the channel forms a liquidmeniscus 20 dividing the channel into a unfilled section 12 a and in afilled section 12 b, shown in a hatched manner in FIG. 1. The unfilledsection 12 a of the channel extends from the inlet 14 to the liquidmeniscus-20, whereas the filled section 12 b of the channel extends fromthe liquid meniscus 20 to outlet 16. In the unfilled section 12 a of thechannel there is preferably air. This section preferably has ambientpressure. Apart from any undesired gas bubbles that may be present, thefilled section 12 b is filled entirely with the liquid 18.

If the inventive liquid reservoir is employed as a drug reservoir inaccordance with its preferred application, the liquid 18 is any drug inthe liquid phase. Alternatively, the inventive liquid reservoir may alsobe used for accommodating other liquids.

In a preferred implementation of the present invention, as is shown inFIG. 1, a capacitive detection principle is employed. For this purpose,two electrodes 22 and 24 are deposited on the base body such that anelectric field, which may be generated between the two electricallyinsulated electrodes, extends both in the filled section 12 b and in theunfilled section 12 a, so that a change in the position of the liquidmeniscus 20 leads to a proportional change in capacitance due to thedifferent relative permittivities of the drug 18 and of the air in theunfilled section 12 a. Depending on the implementation of theelectrodes, of the channel cross-section and of the design of thechannel, a linear connection may be achieved between the change incapacitance and the change in the path of the liquid meniscus 20.

The second but lowest partial image of FIG. 1 shows a cross-sectionthrough the inventive liquid reservoir along the line AA of the secondbut highest partial image of FIG. 1. The inventive liquid reservoirincludes the one electrode 22, which is also referred to as capelectrode due to the representation shown in FIG. 1, as well as theother electrode 24, which is also referred to as bottom electrode. Inaddition, the channel is represented by its unfilled section 12 a and byits filled section 12 b, which is drawn in a hatched manner. Themeandering nature of the channel 12 is expressed by ridges 26 of thebase body, which separate the individual channel sections from eachother. As is shown in FIG. 1, the electrodes 22, 24 are insulated fromthe channel by insulating layers 28, 30, respectively. This is necessaryif the liquid 18 is electrically conductive. If, however, the liquid 18is electrically insulating anyway, the insulating layers 28, 30 may bedispensed with, and the bottom electrode 24 and the cap electrode 22 maydirectly demarcate the channel 12 toward the top and toward the bottom.However, in the case of a drug reservoir, medical aspects are also to betaken into account here with regard to material provisions, materialselection or drug substance, i.e. whether same may be contacted directlywith electrodes to which a voltage is applied.

Finally, the inventive liquid reservoir includes detection means 32which are capacitance measuring means in the preferred embodiment of thepresent invention shown in FIG. 1. Depending on the position x of theliquid meniscus 20 in relation to the channel 12, a capacitance C(x) ismeasured by the detection means 32.

It shall be pointed out at this point that instead of the capacitivedetection means, optical detection means, for example, may also be usedwhich are arranged to scan the channel in a detection passageway, theliquid meniscus being established if either light transmitted throughthe channel or light reflected by the channel floor changes from a highlevel to a low level. In the event of detection means operating in anoptical manner it is necessary, however, that at least the cap or thebottom of the channel 12 be at least partially transparent to thewavelength of the light used. A suitable material for the base body is,for example, the optically transparent material of polycarbonate, whichadvantageously may be processed by injection molding.

Other detection techniques, such as inductive methods, may also be usedas long as the quantity to be measured is influenced by properties ofthe filled section 12 b of the channel compared with properties of theunfilled section 12 a of the channel.

FIG. 2 shows a basic course of capacitance of the capacitance C(x)versus the meniscus position x. The marking x_(full) indicates the casewherein the maximum filling quantity as has been directed has beenfilled into the inventive liquid reservoir. As will be furtherexplained, this is not necessarily the maximum filling quantity.Instead, it is preferred that an unfilled section 12 a of the channelstill remain so as to minimize the evaporation of the liquid. This meansthat the liquid meniscus 20 does not necessarily extend to the outlet 14even with the channel fully filled. The marking x_(empty) shows theposition of the liquid meniscus when the inventive liquid reservoir isemptied as directed. However, the liquid meniscus 20 must notnecessarily be located directly at the outlet 16, if any residual liquidis to remain in the liquid reservoir. In the case of a dielectricconstant of the liquid 18 in the filled section 12 b, which is higherthan the dielectric constant of the medium in the unfilled section 12 a,which usually will be air, the capacitance of the inventive liquidreservoir is the highest when the liquid reservoir has its maximumlevel, as directed. This capacitance value is referred to as C_(full) inFIG. 2. In the opposite case wherein the inventive liquid reservoir isemptied to a maximum, the capacitance, which is still present then, isreferred to as C_(empty). So as to achieve a high sensibility for thepurposes of achieving as good a measuring accuracy as possible, the aimis to maximize C_(full) whereas C_(empty) is minimized. In addition, themeandering length is maximized, depending on the form of application,for achieving as large a filling volume as possible. To this end it isnecessary that the insulating layers 28, 30 (FIG. 1) be selected to beas thin as possible, whereas the meandering area becomes as large aspossible.

From this it can be seen that the demand, which exists on the one hand,for a stable liquid meniscus which is independent of the location, andthe demand, which exists on the other hand, for as large a meanderingarea as possible for achieving a high capacitive sensitivity complementeach other in an optimum manner. Therefore detection means which operatein a capacitive manner are preferred for the inventive liquid reservoir.

The basic concept described in FIG. 1 is disadvantageous with regard tothe fact that both the bottom electrode 22 and the cap electrode 24 arenot optically transparent. Any gas bubbles that may be present in thefilled section 12 b of the channel are not detectable.

To remedy this property, either the cap electrode or the bottomelectrode or both electrodes may be implemented as grid electrodes, sothat the filling quality of the reservoir may be evaluated eithermanually or automatically.

As is shown in FIG. 3, an arrangement of vertical electrodes 22′, 24′may be used instead of the electrodes which extend substantially inparallel with the channel, such that the electrodes are not applied tothe base body 10 as in the embodiment shown in FIG. 1, but are appliedvertically to the main surfaces of the base body. The electrodes 22′,24′ follow, as it were, the channel 12 on both sides of same. If the capof the channel or the bottom of the channel or both, that is cap andbottom, are implemented in an optically transparent manner, it isreadily possible, in this case, to recognize and/or to locate any gasbubbles existing in the filled section 12 b of the channel.

FIG. 4 shows a further variant of the cap electrode 22″ as well as ofthe bottom electrode 24″. Here both electrodes 22″ and 24″ are no longerimplemented as a continuous area but as individual electrode stripsseparated from each other such that an individual capacitance formsbetween an electrode strip of the bottom electrode and an electrodestrip of the cap electrode. By interrogating several electrodes on thetop and bottom sides in pairs, gas bubbles within the filled section 12b of the channel may also be recognized and/or located.

FIG. 5 shows an alternative implementation of the inventive liquidsensor, wherein the base body 10′ is implemented as a hose. On the topside and on the bottom side of the hose, electrodes 22 and 24,respectively, are applied, which are contacted and provided withcapacitive detection means just like in the embodiment shown in FIG. 1,so as to determine the position of the meniscus 20 along the length ofthe hose 10′. It shall be pointed out that in the embodiment shown inFIG. 5 no additional existing insulating layers are required since thewall of the hose itself acts as an insulating layer so as to carry outconductive decoupling of the liquid 18 and the two electrodes 22, 24.

FIG. 6 shows a further implementation of the inventive liquid reservoir,wherein the base body is also implemented as a hose 10′. As opposed tothe embodiment shown in FIG. 5, a coaxial, as it were, electrodearrangement is used in the embodiment shown in FIG. 6. The outer surfaceof the hose 10′ here is fully surrounded by the one electrode 22,whereas the other electrode 24 is formed by a conductor 24 located inthe hose, which conductor 24 is conductively decoupled from the liquid18 by an insulating layer 30′. The electrode 24 may either be loose inthe hose or may be fixed in the center in a concentric manner. If sameis loose in the hose, it is necessary, however, that the drug reservoirin the form of a hose be kept still during dosing system. If itsposition is changed, same must be recalibrated so as to take intoaccount any changes between the insulated inner electrode 24 in relationto the outer electrode 22 arranged on the sheathing of the hose.

In the following, dimensioning criteria of the inventive liquidreservoir, shown in FIG. 1, having a channel which is folded in ameander-like fashion shall be addressed. As has already been explainedwith reference to FIG. 2, the aim is to minimize the empty capacitanceC_(empty) and to maximize the full capacitance C_(full). The emptycapacitance results from connecting in parallel a channel capacitance ofthe channel filled with air and a so-called base body capacitance formedby the frame of the base body and the ridges 26 (FIG. 1) of the basebody. It follows from an examination that for as small an emptycapacitance as possible a material should be used for the base bodywhich has a low dielectric constant. Further it is preferred to keep thesurface areas of the ridges and of the frame as small as possible and/orto apply the electrode only to the channel, if possible, but not toomuch above an area of the base body which is not occupied by thechannel.

The useful capacitance results from the difference between C_(full) andC_(empty). It should be as large as possible. This it achieved by makingthe meandering surface as large as possible in comparison with the areaoccupied by the ridges and the frame. In addition, both the channel capand the channel bottom should be kept as thin as possible, as hasalready been discussed.

In summary, it shall be established that the inventive liquid reservoirwith level measurement is designed such that in the event that thereservoir is emptied, the liquid meniscus which represents the interfacebetween the liquid and air, is guided in a defined manner so that thelevel of the reservoir is measured by suitable detection methods. Thevascular walls of the reservoir are preferably designed such that thediameter of the reservoir is small compared to the length of thereservoir. This may be achieved, on the one hand, by a channel which isfolded in a meander-like fashion or, on the other hand, by a long hose.

A disturbance variable for the level measurement and/or for theoperation of liquid reservoirs altogether is the evaporation of theliquid. It is particularly at the meniscus that the liquid canevaporate. During evaporation, molecules of liquid pass into the gasphase. This effectively leads to a small undesired movement of themeniscus, even though nothing is being dosed. The evaporation rate, i.e.the amount of drugs passing into the gas phase per time unit, above alldepends, in addition to the saturation of air with drug molecules, alsoon the amount of free surface area between drug and air. The smaller thediameter of the channel, the smaller the disturbing evaporation.

The evaporation may have a disruptive effect particularly in the longterm, for example if the reservoir filled is stored over a relativelylong period of time. To further reduce evaporation, suitable measure maybe taken.

One measure is not to fully fill the liquid reservoir, so that asuitably long stretch of air remains. Along this unfilled section of thechannel, a concentration gradient of molecules of liquid that havepassed into the gas phase will form. The longer this diffusion path formolecules of liquid that have passed into the gas phase, the smaller theresulting evaporation will be.

Another measure is to significantly reduce the stretch of air at onelocation, for example to 0.05 mm. Thereby the exchange of moleculesbetween the liquid in the filled section of the channel and the gas inthe unfilled section of the channel is further reduced.

A further measure is to seal the air-side inlet opening with asemi-permeable membrane 15 which is only permeable for air molecules butnot for drug molecules, such that a rapid saturation of the enclosed airwith the drug is achieved. This sealing may entail the further advantageof a germ-free seal, particularly for liquid reservoirs with drugs.

In summary it can therefor be established that the smaller thedimensioning of the channel cross-section is chosen to be, the moresignificant the inventive advantages become. The exact measures,however, will depend on the liquid which is immediately used and on thematerial from which the interior wall of the channel is formed.

A field of application of the liquid reservoir consists in the inventivedosing system comprising, in addition to an inventive liquid reservoir,means for exhausting liquid which may be filled into the liquidreservoir, which means are connected to the outlet, and/or means forpumping gas into the unfilled section, which means are connected to theoutlet. The inventive dosing system further includes control means forcontrolling the means for exhausting and/or the means for pumping, thecontrolling means being coupled to the detection means of the liquidreservoir so as to dispense, depending on the position of the liquidmeniscus, a predetermined amount of liquid from the channel via theoutlet of the channel.

The dosing system may further be converted into a withdrawal system. Inthis case the means connected to the “outlet” are implemented as a pumpso that the liquid to be withdrawn from the body, for example, isconveyed into the liquid reservoir via the outlet. Alternatively, thiscan be a chieved in that the means connected to the inlet areimplemented as suction means.

The dosing system and the withdrawal system may, in accordance with theinvention, further be combined such that in the event of only oneexisting pump/section means same may serve both functions, or that, forexample, a pump only for dosing system is mounted at the inlet, andsuction means only for withdrawing communicate with the outlet.

FIG. 7 shows the inventive dosing system, the inventive withdrawingsystem or the inventive combined dosing/withdrawing system. First ofall, the inventive dosing system is described. In this case, the liquiddosing from the liquid outlet 16 is performed as indicated by an arrow30 in FIG. 7. To this end, block 32 illustrates only a means forexhausting, and block 34 only illustrates a means for pumping. It isclear that in order to perform a liquid dosing, either a means forexhausting in block 32 or a means for pumping in block 34 aresufficient. Naturally, one can also use the means for pumping in block34 as well as the means for exhausting in block 32. The capacitivedetection means performs a detection of the position of the meniscus 20in order to output a level measurement or a change in level measurementto the control means 38. The control means 38 forwards a control signaleither to the means for pumping in block 34 or to the means forexhausting in block 32 or to the means for pumping in block 34 as wellas the means for exhausting in block 32. The control means is operativeto provide the control signal dependent on the level measurement or thechange in level measurement and the predetermined liquid dosing amount.

Alternatively, the inventive device in FIG. 7 can also serve as a liquidwithdrawal apparatus as indicated by arrow 40. In this case, thesituation is contrary to the situation, when the device functions as aliquid dosing system. This means that block 32 only includes the meansfor pumping the predetermined withdrawal amount from the outside intothe channel.

Alternatively, block 34 includes only the means for exhausting gas fromthe channel which also results in a movement of the meniscus 20 fromleft to right, so that the channel includes more liquid after thewithdrawal action compared to the case before the withdrawal action. Asin the dosing device, liquid withdrawal can also be performed by themeans for exhausting gas from section 12 a of the channel as well as themeans for pumping liquid into outlet 16 as indicated in block 32.

In the third embodiment of the present invention, the invention deviceis a combined dosing/withdrawal device. In this case, block 32 includesthe first means for exhausting liquid from the outlet to perform dosing.Alternatively, the device only includes the first means for pumping gasinto the section 12 a of the channel to perform an outlet of liquid atthe liquid outlet 16. Additionally, block 32 can also include the secondmeans for exhausting gas from section 12 a of the channel to performwithdrawal of liquid into the channel. The withdrawal operation can alsobe performed by the second means for pumping in block 32 either inaddition to the second means for exhausting or instead of the means forexhausting.

To summarize, all embodiments have in common that the capacitivedetection means detects the position of the meniscus in order to outputa level measurement or a change in level measurement which is input intothe control means 38 which, depending on the level measurement and thechange in level measurement as well as the predetermined liquid dosingamount or the predetermined liquid withdrawal amount forwards respectivecontrol signals to block 34 or 32.

1. Dosing system for dosing a predetermined amount of liquid,comprising: a liquid reservoir with level measurement, comprising: abase body; a channel implemented in the base body and having an inletand an outlet, the dimensions of a cross-section of the channel beingselected such that a liquid when filled into the channel forms a liquidmeniscus which demarcates a section of the channel filled with liquidfrom an unfilled section of the channel in which no liquid is present,wherein the dimensions of the cross-section of the channel, the liquidand a material of the channel are selected such that the position of theliquid meniscus in relation to the channel being substantiallyindependent of the orientation of the liquid reservoir; and detectionmeans for detecting the position of the liquid meniscus in relation tothe channel so as to obtain a level measurement or a change in levelmeasurement of the liquid reservoir by detecting the position of theliquid meniscus; means for exhausting the predetermined amount ofliquid, the means for exhausting being connected to the outlet of thechannel, or means for pumping gas into the unfilled section of thechannel, the means for pumping being connected to the inlet of thechannel; and control means for controlling the means for exhausting andthe means for pumping, the control means coupled to the detection meansof the liquid reservoir so as to obtain the level measurement or thechange in level measurement and to control the means for exhausting andthe means for pumping to dispense the predetermined amount of liquidfrom the channel via the outlet of the channel, depending on the levelmeasurement or the change in level measurement; wherein the detectionmeans are capacitive and comprise two electrodes electrically insulatedfrom each other and mounted on the base body such that both the filledand the unfilled section of the channel extend between same, wherein anelectric field to be generated between the two electrodes is presentboth in the filled section of the channel and in the unfilled section ofthe channel, and wherein a change in the position of the liquid meniscusleads to a proportional change in capacitance.
 2. Withdrawal system forwithdrawing a predetermined amount of liquid, comprising: a liquidreservoir with level measurement, comprising: a base body; a channelimplemented in the base body and having an inlet and an outlet, thedimensions of the channel cross-section being selected such that aliquid when filled into the channel forms a liquid meniscus whichdemarcates a section of the channel filled with liquid from an unfilledsection of the channel in which no liquid is present; wherein thedimensions of the cross-section of the channel, the liquid and amaterial of the channel are selected such that the position of theliquid meniscus in relation to the channel being substantiallyindependent of the orientation of the liquid reservoir; and detectionmeans for detecting the position of the liquid meniscus in relation tothe channel so as to obtain a level measurement or a change in levelmeasurement by detecting the position of the liquid meniscus; means forpumping a liquid into the liquid reservoir the means for pumping beingconnected to the outlet of the channel, or means for exhausting gas fromthe unfilled section of the channel exhausting being connected to theinlet of the channel; and control means for controlling the means forpumping and the means for exhausting, the control means being coupled tothe detection means of the liquid reservoir so as to obtain the levelmeasurement or the change in level measurement and to control the meansfor exhausting and the means for pumping to convey a predeterminedamount of liquid into the channel via the outlet of the channeldepending on the level measurement or the change in level measurement;wherein the detection means are capacitive and comprise two electrodeselectrically insulated from each other and mounted on the base body suchthat both the filled and the unfilled section of the channel extendbetween same, wherein an electric field to be generated between the twoelectrodes is present both in the filled section of the channel and inthe unfilled section of the channel, and wherein a change in theposition of the liquid meniscus leads to a proportional change incapacitance.
 3. Dosing system as claimed in claim 1, wherein the channelis folded in a meander-like fashion so as to obtain a comparatively longchannel in relation to outer dimensions of the base body.
 4. Dosingsystem as claimed in claim 1, wherein the base body is a hose, and thechannel is formed by the opening of the hose.
 5. Dosing system asclaimed in claim 1, wherein the channel has elliptical and preferablycircular cross-sectional dimensions, the small axis of the ellipticalcross-section and/or the diameter of the circular cross-section beingselected to be so small that the position of the meniscus is determinedsubstantially by the surface tension of the liquid as well as by theinterfacial tension between the liquid and the material of the channelwall, whereas gravity has substantially no influence on the position ofthe meniscus.
 6. Dosing system as claimed in claim 1, wherein thechannel has rectangular cross-sectional dimensions, the small side ofthe rectangular cross-sectional dimensions being selected so small thatthe position of the meniscus is determined substantially by the surfacetension of the liquid as well as by the interfacial tension between theliquid and the material of the channel wall, whereas gravity hassubstantially no influence on the position of the meniscus.
 7. Dosingsystem as claimed in claim 1, wherein the length of the channel isselected such that, with the liquid reservoir filled as directed, thesection of the channel in which no liquid is present has a minimumlength determined by an admissible evaporation rate for the liquid. 8.Dosing system as claimed in claim 1, wherein in the section of thechannel in which no liquid is present, with the liquid reservoir filledas directed, a constriction is present, the cross-sectional dimensioningof which is influenced by admissible evaporation rate.
 9. Dosing systemas claimed in claim 1, wherein a sealing in the form of a semi-permeablemembrane which is impermeable for liquid molecules is present at theinlet.
 10. Dosing system as claimed in claim 1, wherein the base body isa hose, and wherein both electrodes are arranged on the outer surface ofthe hose and extend along the length of the hose.
 11. Dosing system asclaimed in claim 1, wherein the base body is a hose, and wherein oneelectrode is arranged on the outer surface of the hose, and the otherelectrode is positioned within the hose and is separated from the liquidby an insulating layer by means of conductive separation.
 12. Dosingsystem as claimed in claim 1, wherein one electrode is implemented as abottom electrode, and wherein the other electrode is implemented as acap electrode, the channel present in the base body being directlybounded by the bottom and cap electrodes or being bounded by anelectrically insulating layer between the bottom electrode and thechannel and by an electrically insulating layer between the capelectrode and the channel, the electrically insulating layers beingimplemented integrally with the base body and/or the bottom and capelectrodes.
 13. Dosing system as claimed in claim 12, wherein the capelectrode, the bottom electrode or both are implemented as gridelectrodes so as to be able to optically detect any gas bubbles in thefilled section of the channel.
 14. Dosing system as claimed in claim 12,wherein the cap electrode and/or the bottom electrode consist of aplurality of individual electrodes, so that a plurality of individualcapacitances are formed between the bottom electrode and the capelectrode, the individual capacitances being determinable independentlyof each other so as to capacitively detect any gas bubbles in the filledsection.
 15. Dosing system as claimed in claim 1, wherein bothelectrodes are arranged vertically in relation to main surfaces of thebase body and each extend along the channel.
 16. Dosing system asclaimed in claim 1, wherein the detection means are arranged so as tooptically monitor the level in the channel, and wherein the channel isoptically transparent on at least one side of same so that an evaluationof the filling quality is to be performed manually or automatically. 17.Combined dosing/withdrawal system for dosing a predetermined amount ofliquid or for withdrawing a predetermined amount of liquid, comprising:a liquid reservoir with level measurement, comprising: a base body; achannel implemented in the base body and having an inlet and an outlet,the dimensions of the channel cross-section being selected such that aliquid when filled into the channel forms a liquid meniscus whichdemarcates a section of the channel filled with liquid from an unfilledsection of the channel in which no liquid-s present; wherein thedimensions of the cross-section of the channel, the liquid and amaterial of the channel are selected such that the position of theliquid meniscus in relation to the channel being substantiallyindependent of the orientation of the liquid reservoir; and detectionmeans for detecting the position of the liquid meniscus in relation tothe channel so as to obtain a level measurement or a change in levelmeasurement by detecting the position of the liquid meniscus; firstmeans for pumping a liquid into the liquid reservoir or for exhausting aliquid from the liquid reservoir, the first means for pumping orexhausting being connected to the outlet; second means for exhaustinggas from the unfilled section of the channel or for pumping gas into theunfilled section of the channel the second means for exhausting orpumping being connected to the inlet; and control means for controllingthe first means and the second means, the control means being coupled tothe detection means of the liquid reservoir so as to obtain the levelmeasurement or the change in level measurement and to control the meansfor exhausting and the means for pumping to convey the predeterminedamount of liquid into the channel via the outlet of the channel or todispense the predetermined amount of liquid from the channel via theoutlet of the channel, depending on the level measurement or the chancein level measurement; wherein the detection means are capacitive andcomprise two electrodes electrically insulated from each other andmounted on the base body such that both the filled and the unfilledsection of the channel extend between same, wherein an electric fieldthat may be generated between the two electrodes is present both in thefilled section of the channel and in the unfilled section of thechannel, and wherein a change in the position of the liquid meniscusleads to a proportional change in capacitance.